1. Field of the Invention
This invention relates to the removal of hydrogen sulfide from gases, and more particularly to a process for removing hydrogen sulfide from hydrogenated Claus process tail gas in which the hydrogen sulfide is converted to elemental sulfur.
2. Description of the Prior Art
With the increasing concern over the pollution of the atmosphere, great demands have heen made on industry to produce pollution-free products and to do so in a pollution-free manner. One area of particular concern has been the release of sulfur and its compounds into the atmosphere during petroleum refining, natural gas sweetening, ore processing, coke-oven gas production, and the production of other sulfur-containing gases.
One such process for treating hydrogen sulfide-containing gas which has been used in conjunction with the desulfurization of hydrogen sulfide-containing gases, known as the Claus process, is about 90 to 97 percent effective in converting hydrogen sulfide to elemental sulfur. In many instances it is necessary to further treat the Claus process tail gas to make it acceptable for discharging into the atmosphere. One process particularly useful for treating these tail gases is the Beavon sulfur removal process described in U.S. Pat. No. 3,752,877 which involves the hydrogenation of the Claus process tail gas, to convert the various sulfur compounds to hydrogen sulfide, and then employing a process, known as the Stretford process, to remove the remaining hydrogen sulfide. The Stretford process is a well-known process for converting hydrogen sulfide to elemental sulfur and is generally described in U.S. Pats. Nos. 2,997,439, 3,035,889, and 3,097,926.
However, while the Stretford process has been relatively successful, it has been discovered that when used to treat hydrogenated Claus process tail gas, one of the principal constituents of the Stretford solution, an anthraquinone disulfonate, was being chemically consumed; and this consumption necessitated frequent addition of this expensive chemical. It is to the consumption of anthraquinone disulfonate (ADA) and to the improvement of the Stretford process that this invention is directed.
A principal object of this invention is to provide an improvement in the Stretford process for the removal of hydrogen sulfide from gases and its conversion to elemental sulfur.
Another object of this invention is to provide an improvement in the Stretford process when used to treat hydrogenated Claus process tail gas.
Yet another object of this invention is to reduce the excessive amounts of ADA consumed by oxidation in a Stretford unit used to treat hydrogenated Claus process tail gas.